How do you prevent neck injuries?

Hi,
i am training for the last 3 years no gi and 1,5 bjj. i had neck injuries before - in most of the cases you just feel like a robot for a week and thats it. i would get them once in every few months. Recently after every single training i am in pain... i have no idea what changed but its not good. do you have any ideas how to avoid neck injuries?
before every training i am stretching and warming it up but i feel thats not enough.

Strengthen your neck regular exercise, it will reduce the frequency of injuries at least. Also tell people about it before you roll so they aren't overly aggressive with collar chokes etc. And keep well away from well known head squeezers

I suffer with my neck and have done for over 9 years, I was dropped on my head and didn't bother to get it checked out. Get an mri just to be safe, if there's already disc damage you don't want to be making it worse. Two of my friends who train bjj have both just had surgery

OLD SCHOOL CARLSON GRACIE NECK STRENGTHENING ROUTINE-
Frequency- EVERY DAY (for Casca Grossa's twice per day).

Lie on the floor on your back.
Lift your head off the floor-IMPORTANT-do not let it touch the floor again until finished.
Nod your head forward (imagine an ab crunch but using your neck instead of your core) repeat 100 times.
Look left and right 100 times.
Tilt your head towards each of your ear's 100 times.
Finish.
So the set is 300 reps.

Wrestling neck bridges. Its more of a preventative measure rather than if you are already injured, but if you do bridges and strengthen your neck in the first place you will be less likely to be injured in the future.

I went into BJJ with a lot of scar tissue in my neck from a serious rugby accident, and a subsequent car accident. My neck was really tight, would get impingement, pain and it was weak as hell.

I had loads of scans and so forth to make sure there was no damage to physical architecture of my neck, so if you have not already had this I would highly recommend it. I had a course of physio after my rugby accident, and then had a course of private physio after my car accident (however, I know this option is not available to everyone it was simply due to my circumstances at the time). I have maintained a regime of soft tissue work after this which has all but gotten rid of the scar tissue build up in my neck.

For me personally, I did a lot of strengthening work very similar to the outline Simon gave, and that worked really well for me. Since then, I have found just training has helped a lot, and compound exercises like deadlifts and pull-ups. Manofearth recommended wrestling bridges, personally I avoided these as I was already injured as the hyperextension results in masses of intravertebral pressure and in my case was just asking for a herniation. I do them now (sparingly, as my weight goes between 100-110kg) but as manofearth rightly said they can be good if done with a healthy neck by the right person.

In summary; you only have one neck, look after it! If you are now in pain after "every single training" and it "takes all the fun away" I would say it's time to get it checked out!

The beauty of the Carlson routine is that the only resistance is the weight of your head,and obviously
our necks were designed to lift the weight of our heads.The moment you add more resistance (ie extra weights or wrestling bridges) the ability to get stronger is increased,but so is the risk of neck injury- which ironically is the very thing we are trying to avoid in the first place.
I am not being negative about wrestling bridges-just stressing that unless your neck is 100% healthy they may not be a good idea.